1. Field of the Invention
The present invention relates to hole cutting devices, and more particularly to powered hole cutters enclosed in a suction chamber for collecting the cutting dust in the course of forming an inspection aperture in asbestos insulation cladding.
2. Description of the Prior Art
For some time containment vessels were covered with insulative layers including asbestos. The fire resistive qualities of asbestos, its availability in nature, and the insulative qualities all combined to a preference, and large numbers of storage tanks and vessels are now insulated with asbestos cladding. Until now the exterior skin of the cladding served as a containment mechanism, and as the carcinogenic aspects of asbestos became known this exterior skin structure served as the excuse and attenuation of the public concern over the health hazards of this earlier practice.
Nonetheless, the maturation process of of tank structures brought with it the processes of corrosion, and concern over the integrity of the vessel wall is now at the forfront. For this reason a variety of techniques have been devised in the art to form acces openings in the insulation cladding, including those exemplified in the teachings of U.S. Pat. No. 5,010,926 to Kurth et al, and others. While suitable for the purposes intended, these and the other references deal with the structure of the aperture itself, but fail to address the health risks to those engaged in the forming of the aperture. More precisely, the release to the surrounding environment of the asbestos particulate debris in the course of forming the aperture has had little attention, a release that poses some risks to the employees engaed in the task.
For example, Cal/OSHA interfaces with the General Industry Safety Orders GISO! setting out comprehensive standards governing work with asbestos, GISO 5208!. These are then complkemented with various labor codes, e.g., California Labor Code Sections 6501.5 et seq. Thus extensive regulatory enactments are in place, that need corresponding accomodation in the tools utilized.
At the same time, various structures and techniques have been devised in the art for collecting the cutting dust in the course of powered shaping and forming of structures. Typically such collection mechanisms take the form of an evacuated collection enclosure surrounding the cutting tool end, and an evacuation pump to draw the cutting dust from the enclosure onto a filter. Examples of such prior art mechanisms may be found in U.S. Pat. Nos. 5,292,210 to Nowick; 4,968,189 to Pidgeon; 4,921,375 to Famulari; and 3,033,298 to Johnson; German patent DE 3,126,511 A1 to Buschbaum; German patent DT 2,453,791 to Bengt; French patent 916,861; and British patent 2,096,030 to Rohm. Each of the foregoing, while suitable for the purposes intended, fails to address the pernicious nature of asbestos, and the health risks posed thereby.
A technique controlling the release of the particulate matter, and the consequent potential of the inhalation or absorption thereof, is therefore desired and it is one such technique that is described herein.